/* ====================================================================
 * The Apache Software License, Version 1.1
 *
 * Copyright (c) 2001 The Apache Software Foundation.  All rights
 * reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 *
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in
 *    the documentation and/or other materials provided with the
 *    distribution.
 *
 * 3. The end-user documentation included with the redistribution,
 *    if any, must include the following acknowledgment:
 *       "This product includes software developed by the
 *        Apache Software Foundation (http://www.apache.org/)."
 *    Alternately, this acknowledgment may appear in the software itself,
 *    if and wherever such third-party acknowledgments normally appear.
 *
 * 4. The names "Apache" and "Apache Software Foundation" and
 *    "Apache Lucene" must not be used to endorse or promote products
 *    derived from this software without prior written permission. For
 *    written permission, please contact apache@apache.org.
 *
 * 5. Products derived from this software may not be called "Apache",
 *    "Apache Lucene", nor may "Apache" appear in their name, without
 *    prior written permission of the Apache Software Foundation.
 *
 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED
 * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
 * DISCLAIMED.  IN NO EVENT SHALL THE APACHE SOFTWARE FOUNDATION OR
 * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
 * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
 * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 * ====================================================================
 *
 * This software consists of voluntary contributions made by many
 * individuals on behalf of the Apache Software Foundation.  For more
 * information on the Apache Software Foundation, please see
 * <http://www.apache.org/>.
 */

using System;

namespace DotnetPark.NLucene.Index
{
	internal class SegmentsTermEnum : ITermEnum 
	{
		private SegmentMergeQueue queue;

		private Term term;
		private int docFreq;

		internal SegmentsTermEnum(SegmentReader[] readers, int[] starts, Term t)
		{
			queue = new SegmentMergeQueue(readers.Length);
			for (int i = 0; i < readers.Length; i++) 
			{
				SegmentReader reader = readers[i];
				SegmentTermEnum termEnum;

				if (t != null) 
				{
					termEnum = (SegmentTermEnum)reader.Terms(t);
				} 
				else
					termEnum = (SegmentTermEnum)reader.Terms();
      
				SegmentMergeInfo smi = new SegmentMergeInfo(starts[i], termEnum, reader);
				if (t == null ? smi.Next() : termEnum.Term() != null)
					queue.Put(smi);				  // initialize queue
				else
					smi.Close();
			}

			if (t != null && queue.Size() > 0) 
			{
				SegmentMergeInfo top = (SegmentMergeInfo)queue.Top();
				term = top.TermEnum.Term();
				docFreq = top.TermEnum.DocFreq();
			}
		}

		public bool Next() 
		{
			SegmentMergeInfo top = (SegmentMergeInfo)queue.Top();
			if (top == null) 
			{
				term = null;
				return false;
			}
      
			term = top.Term;
			docFreq = 0;
    
			while (top != null && term.CompareTo(top.Term) == 0) 
			{
				queue.Pop();
				docFreq += top.TermEnum.DocFreq();	  // increment freq
				if (top.Next())
					queue.Put(top);				  // restore queue
				else
					top.Close();				  // done with a segment
				top = (SegmentMergeInfo)queue.Top();
			}
			return true;
		}

		public Term Term() 
		{
			return term;
		}

		public int DocFreq() 
		{
			return docFreq;
		}

		public void Close() 
		{
			queue.Close();
		}
	}
}
